This invention relates to apparatus for handling sheets of cardboard, card or the like particularly prior to or subsequently to processing of such sheets by for example a die-cutter machine.
According to one aspect of the present invention we provide sheet handling apparatus comprising a conveyor belt drive, suction means for drawing a sheet against a lower run of said belt drive to enable the sheet to be conveyed by the belt drive, at least one sheet-engaging element movable between an upper position at or above the plane of said lower run and a lower position below said plane, and drive means for effecting such movement of said at least one element, characterised in that said drive means is operable to impart to said at least one element a component of velocity in the direction of travel of said lower run, which velocity component is at least momentarily substantially the same as the belt speed when said at least one element is immediately below the plane of said lower run.
Although the invention is considered to be applicable to feeding of sheets from a stack to processing machinery, the primary application of the invention is in stacking sheets as they are fed from processing machinery. Our prior British Pat. No. 1,340,004 shows one form of sheet stacking apparatus which solves many of the problems encountered with the stacking of continuously-fed fragile die-cut sheets. In particular, the integrity of the fragile sheets is maintained during transfer from the die-cutting station to the stacking station by synchronising the speed of the belts at the latter station with the sheet feed speed during transfer and then slowing the belts before ejecting the sheets onto the stacking table. However the time lost in slowing the belts and also in moving the ejector arms vertically upwardly and downwardly, imposes limits on the maximum length of sheet that can be fed in relation to the die cutter because the spacing between successive sheets must be sufficient to account for these losses in time.